Alien Worlds
The Search for Other "Earths"

Thursday, February 9th, 2006
We stand ever closer to the point in human development when we will learn whether we are alone in the Galaxy, or likely to be part of a teeming community of planets with life on them.
Dr. Gibor

Professor of Astronomy
University of California
at Berkeley

Gibor Basri received a BSc in Physics from Stanford Univ. in 1973, and a PhD in Astrophysics from the Univ. of Colorado, Boulder in 1979. His work in the 1980s concentrated on star formation and the study of T Tauri stars, as well as continuing studies of stellar activity. In the past decade he has continued work on these topics, as well as becoming a world expert in the study of  brown dwarfs. He wrote an Annual Reviews of Astronomy and Astrophysics article on "Observations of Brown Dwarfs" in 2000, and delivered a plenary lecture to the American Astronomical Society entitled "Brown Dwarfs: Up Close and Physical" in 2004.

He has written numerous review articles, along with well over 100 technical publications. GB was awarded a Miller Research Professorship in 1997, and became a Sigma Xi Distinguished Lecturer in 2000. He has served on committees helping to award major NASA and NSF grants and projects, and awarding time on the (world's largest) Keck telescopes. He is increasingly involved in science education, and encouraging the participation of minorities in science. One such effort is service on the Board of the Chabot Space and Science Center.

During the last decade, astronomers have finally begun finding planets around other stars. We still don't know how common they are, and we know nothing about the number of planets like the Earth (none of the planets found so far are likely to even have a surface you could stand on). Professor Basri will describe what we have learned so far, and what we think we know about planet formation, which suggests that terrestrial planets should be common. He is involved in the new NASA mission named "Kepler", which intends to directly answer the question by finding many such planets. This dedicated space telescope should be launched in the next few years, and will monitor more than 100,000 stars.  It looks for the telltale dip in their light caused if a planet crosses in front of them (the "transit" method, which is currently the best way to find Earth-sized planets). Professor Basri will describe this exciting mission, and evaluate its chances for success.

The Kepler mission should make an inventory of planets down to the size of Mars in the inner planetary systems where the "habitable zone" lies. He will explain what this zone is, and how it depends on what sort of star the planet orbits. In thinking about where life may actually exist on other planets, we may need to broaden our thinking well beyond what we experience here at the surface of this Earth. We stand ever closer to the point in human development when we will learn whether we are alone in the Galaxy, or likely to be part of a teeming community of planets with life on them.

In December 2001, NASA selected the Kepler mission as one of its next Discovery missions. This mission has as its goal the discovery of extrasolar terrestrial planets, and the characterization of all planets in inner solar systems.

This mission will launch a 1-meter telescope (perhaps in 2006) whose purpose is to detect transits caused by terrestrial planets around other stars. It will watch 100,000 stars continuously (every 15 minutes) for at least 4 years, with a photometric precision of one part in 50,000. It should see all the inner planets whose orbital planes cause eclipses for us, and also reflected light from giant inner planets. It is capable of finding "true Earth analogs" (planets with 1 Earth mass in 1 year orbits around Sun-like stars).

As co-investigator, Dr. Basri's role in the project is to understand the photometric variations caused by the stars themselves - this will be a huge collateral windfall of stellar science which is a natural side-effect of the main mission.

The Kepler Mission website

Gibor Basri's Contributions to the Study of Brown Dwarfs and Low Mass Stars
A treatment can be found in my article in Scientific American (April 2000).